Java.Hibernate.Beginner.What is the purpose of the @Entity annotation?

The @Entity annotation marks a Java class as a persistent entity in JPA/Hibernate, meaning it should be mapped to a table in the database.
It tells the JPA provider (Hibernate) to manage instances of the class as rows in a relational table.

🔹 What does @Entity do?
✅ Registers the class as part of the persistence context → Hibernate will map it to a database table.
✅ Enables automatic ORM (object-relational mapping) → Hibernate translates Java objects into SQL statements for CRUD operations.
✅ Ensures the class participates in JPA features like transactions, caching, dirty checking, and queries.

🔹 Basic example:

import javax.persistence.Entity;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String username;
}

✅ Here:

• User is an entity → each instance of User corresponds to a row in a table (e.g., users).
• Fields in User map to columns in the table.

🔹 Important notes:
✅ Every @Entity class must have a primary key, defined with @Id.
✅ You can specify a custom table name with @Table(name = "your_table"), but if omitted, the table defaults to the class name.

🔹 Why is it important?
Without @Entity, Hibernate/JPA ignores the class → it won’t be mapped to a table, persisted, or managed.

✅ Key takeaway:
@Entity marks a Java class as a persistent entity mapped to a database table, enabling Hibernate or any JPA provider to manage it automatically.